[dcl.attr.grammar] Fix "ill formed" and "malformed".

Hyphenate ill-formed.
Use "invalid" instead of "malformed" to avoid confusion.

Fixes #59.
Remove trailing whitespace
[dcl.type.simple] Fix example.

Use an rvalue instead of an lvalue in the example.

Unlike the issue suggested I did not remove the declaration of i,
since it's still used in the x2 example.

Fixes #60.
[vector.bool] Add missing close paren in synopsis.

Fixes #62.
[ratio.ratio] Move ratio::type after the types it uses.

Fixes #67.
[lex.header], [lex.string] Hyphenate conditionally-supported.

Fixes #68.
[pairs.pair] Remove duplicate "Requires:".

Fixes #70.
[memory.syn] Add missing declarations.

Add make_shared() and allocate_shared() declarations to the <memory>
synopsis.

Fixes #71.